1. Field of the Invention
The invention relates to a gas-cooled electric machine having a rotor, a stator and a housing surrounding the stator, having one or two stator winding bars which are located one above the other in a groove, are built up from mutually insulated component conductors and are connected to one another electrically and mechanically outside the stator core assembly in the overhang space by means of metallic lugs to form a winding, and having essentially radial slots or ducts in the stator through which cooling gas can be led and a fan on each machine side whose suction chamber is separated by a partition from the overhang space.
In this regard, the invention refers to a prior art such as emerges, for example, from the journal BROWN BOVERI TECHNIK 3-86, page 135.
2. Discussion of Background
In electric machines having an indirectly cooled stator winding, the gas flow which leaves the fan and passes through the winding overhang has so far been sufficient to cool the front brackets in the winding overhang, and especially the lugs which connect the individual conductor bars electrically and mechanically to the actual coil. In limit-rating machines, the winding overhangs and lugs can be endangered by excessive heating. Whereas the part of the winding embedded in the winding grooves is cooled in a targeted fashion, these exposed winding parts, as well as the lugs, are heated not only by the current flow but also by the electromagnetic fields in the overhang space. Particularly endangered in this case is the insulation in the region of the lugs and--if the lugs are not hard-soldered--the entire construction of the connecting conductors and the lugs.